I sincerely hope that the Tories don't marshal some economists of their own. The last time that happened, back in February, we witnessed the low point of the fiscal debate – with both sides using a bunch of academics as a substitute for a proper conversation with the public. And, lest we forget, Guido's handy graph reminds us just what those economists were and are quibbling over anyway. This is a phoney war, so it's little surprise that Brown has resorted to it once again.
Thankfully, signs are that Tories won't pay heed to the bait. Not just because they've been there, done that. But because they're quite happy with their signatures from businessmen over national insurance, thank you very much. Indeed, reports say that Brown failed to gather his own group of businessmen for this letter – so had to settle for economists instead. For the Tories, the idea that businessmen disagree with Labour, and agree with them, is much more powerful than the idea that some economists disagree with each other.
Even so, you can be sure Brown will try to mention the letter during tonight's TV debate. In which case, I expect the Cameron script will
"So what? (As your Schools Secretary might say). We had our own letter a few months ago, with economists backing our plans for cuts. Economists disagree – I thought you'd know that.
But – and this is the crucial point – you haven't been able to get businessmen to back your tax on jobs. That's because they don't want to. I've spoken with hundreds of businessmen, up and down the country, who oppose your tax hike – and who support Conservative plans to cut it.
Yes, businessmen disagree. They all disagree with you."
Or words to that effect.